1. Field of the Invention
The present invention relates to a cardiac mapping probe and more particularly to a lead body having electrodes at the distal end thereof which are used in intrasurgical cardiac mapping.
2. Description of the Prior Art
Cardiac mapping is used to locate aberrant electrical pathways within the heart which cause the contractions of the heart muscle to take on peculiar and life threatening contractile patterns.
In the ordinary healthy human heart, contractions begin with a wave of electrical excitation beginning in the right atrium, spreading to the left atrium, and thence to the A-V node which slows down the electrical excitation and then passes it down to what is known as the bundle of His (a bundle of conductive heart muscle fibers) leading into the ventricles. However at times, due to what are generally regarded as congenital anomalies, conductive atrioventricular pathways called accessory pathways of atrioventricular conduction, left over, from the time of embryonic cardiac development, become active in a patient's life. Such pathways, known also as Kent bundles, cause disruption of the normal beat by allowing electrical stimulation of the ventricle to occur through the Kent bundle directly or through re-entry via the Kent bundle into the A-V node at a time inappropriate to the normal cardiac cycle.
Correction of the resultant arythmias or tachicardias is usually accomplished through the surgical disruption of the Kent or His bundle and through the employment of cardiac pacing in some cases.
The only known method for locating Kent bundles is through a procedure called cardiac mapping. Mapping is currently accomplished by dividing the entire ventricular surface of the heart into 53 imaginary sections which are "mapped" electrically using both unipolar and bipolar electrodes and a reference electrode. The unipolar and bipolar electrodes are manually moved about the surfaces of the heart for completely mapping the activation sequence throughout the heart.
There are several different specialized electrodes commonly used for cardiac mapping. By the mere fact of their multiplicity, operating room, surgical and recordation procedures are unnecessarily complicated. A representative group of probes consists of a slightly curved probe, a strongly curved probe and a finger attached set of three bipolar probes, which can, in combination, reach any area of the heart.
Where in certain cases, it is desirable to map an interior portion of the heart, a large incision must be made to facilitate the entry of these probes into the heart. Examples of these probes are illustrated on page 856 of Circulation Volume 57, No. 5, May 1978 in an article devoted to epicardial mapping by Gallagher, et al.
Aside from the complications involved with the above described probes is the concomitant difficulty in manipulating them into and maintaining them in position during mapping. Usually, such probes have only two electrical contact points apiece making determination of the direction and velocity of the flow of activity from a single probe position impossible.
Examples of previously proposed cardiac mapping probes and methods for mapping are disclosed in the following U.S. patents and articles:
______________________________________ U.S. PAT. NO. PATENTEE ______________________________________ 3,313,293 J. A. Chesebrough et al 4,044,774 Terry Corbin et al 4,125,116 Robert E. Fischell 4,341,221 Roy L. Testerman 4,374,527 Alfred A. Iversen ______________________________________ "Effectiveness of Surgical Management of the WolffParkinson-White Syndrome", Will C. Sealy, M.D., The American Journal of Surgery, June 1983, Vol. 145, 756. "Selection of Site for Permanent Epicardial Pacing Using Myocardial Testing Electrode", Varriale et al, New York State Jrnl. of Medicine, Jul 1977, 1272. "Epicardial Mapping in the WolffParkinson-White Syndrome", Gallagher et al, Circulation, Vol. 57, No. 5, 854, May 1978.
As will be described in greater detail hereinafter, the cardiac mapping probe of the present invention differs from the previously proposed probes by providing a multiple electrode single probe having a lead body which is moldable, pliable and formable into a variety of shapes which it will hold until remolded and reformed.
The single probe design obviates the complicity in surgical and recordation procedures which stem from the extra wiring and sterilization required for a multiplicity of probes. At the same time, the moldable shape of the lead body eliminates the complicated mechanical contortions required to effectively utilize non-shapeable and finger-attached probes for mapping. The shape retention property allows the probe to be inserted through a small incision in the myocardium when necessary while holding its shape once positioned, thus removing the necessity of employing larger, finger-attached probes for the task, with a larger incision.
Furthermore, the lead body has a surface which is soft and pliable and designed to minimize tissue damage, while the distal end thereof has four independently wired electrodes which allow for mapping in a way not contemplated nor provided for in the prior art patents and articles referred to above.